The invention concerns an apparatus for mounting semiconductor chips on a substrate which is suitable for mounting semiconductor chips which adhere to a foil clamped into a frame. The invention further concerns a method for mounting semiconductor chips on a substrate.
With such an apparatus, the frame with the foil is accepted by a movable table. The table is moved in cycles so that one semiconductor chip after the other is presented at a first location A and the presented semiconductor chip is then picked by chip gripper and placed on a substrate at a second location B. By means of a measuring camera directed at the first location A, the position of the presented semiconductor chip is measured before removing it from the foil and the deviation of the position from its set position is established and a correction vector is determined. The following methods are known for the correction of the established deviation:
1. After establishing the deviation, however before removal of the presented semiconductor chip from the foil, the table is moved by the correction vector. This method is implemented on one of the machines introduced to the market by the applicant.
2. The correction of the deviation takes place by means of a corrective movement of the chip gripper and/or by means of a corrective movement of the substrate. This method is implemented on a machine newly launched by the applicant.
The removal of the presented semiconductor chip from the foil is supported by a chip ejector (known also as a die ejector) arranged underneath the foil. Removal of the semiconductor chip takes place in that the foil is sucked onto and secured by the chip ejector by means of vacuum and in that subsequently, optionally, a needle penetrating the foil from underneath pushes the semiconductor chip against the suction opening of the chip gripper.
When now, in accordance with the first method mentioned above, the table is moved by the correction vector, then the friction between the foil and the chip ejector can lead to the position of the semiconductor chip still deviating by some micrometres from the set position after the corrective movement. The foil lies namely with a certain weight on the chip ejector. With small corrective movements which amount to only a few micrometres, the friction between the foil and the chip ejector now has the effect that with such small correction movements the foil does not follow the movement of the table but simply stretches.
With the second method, the necessary accuracy for placement of the semiconductor chip on the substrate can be achieved, however the solution is technically very expensive.
The object of the invention is to overcome the disadvantages of the prior art.
An apparatus for mounting semiconductor chips on a substrate, with which the semiconductor chips on a foil clamped in a frame are presented at a first location A, comprises a chip gripper for the transport of the semiconductor chip presented at the first location A to a second location located on a substrate, a movable table for acceptance of the frame, a chip ejector arranged underneath the foil at the first location A the upper surface of which facing the foil has a hole connected to a vacuum source, as well as a measuring camera directed at the first location A for establishing the position of the presented semiconductor chip. The correction of a possible position deviation of the presented semiconductor chip from its set position takes place in accordance with the invention in that the foil is secured by the chip ejector by means of vacuum and then at least the upper surface of the chip ejector facing the foil is moved in the plane running parallel to the underneath of the foil.